| triangle of safety | The area at the lower left sternal border where the pericardium is not covered by lung (pericardial notch); preferred site for aspiration of pericardial fluid. (05 Mar 2000) |
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| triangle of vertebral artery | <anatomy, artery> Triangular area in the root of the neck bounded laterally by the scalenus anterior and medially by the longus coli muscles; the two muscles meet at the triangle's apex, formed by the anterior (carotid) tubercle of the transverse process of vertebra C6; the vertebral artery arises from the subclavian artery at the base of the triangle, bisecting the triangle as it ascends to the apex to enter the transverse foramen of vertebra C6. (05 Mar 2000) |
| Tweed triangle | A triangle defined by facial and dental landmarks on a lateral cephalometric film, using the Frankfort horizontal plane as a base and intended for use as a guide in the evaluation and planning of orthodontic treatment. (05 Mar 2000) |
| facial triangle | A triangle formed by lines connecting the basion, the prosthion, and the nasion. (05 Mar 2000) |
| Farabeuf's triangle | The triangle formed by the internal jugular and facial veins and the hypoglossal nerve. (05 Mar 2000) |
| umbilicomammillary triangle | A triangle with its apex at the umbilicus and its base at the line joining the nipples. (05 Mar 2000) |
| Killian's triangle | <anatomy> The triangular-shaped area of the cervical oesophagus bordered by the oblique fibres of the inferior constrictor muscle of the pharynx and the transverse fibres of the cricopharyngeus muscle through which Zenker's diverticulum occurs, and the A-V nodal triangle between the coronary sinus orifice and the ventricular crest. Synonym: laimer triangle. (05 Mar 2000) |
| femoral triangle | A triangular space at the upper part of the thigh, bounded by the sartorius and adductor longus muscles and the inguinal ligament, with a floor formed laterally by the iliopsoas muscle and medially by the pectineus muscle; the branches of the femoral nerve are distributed within the femoral triangle; it is bisected by the femoral vessels, which enter the adductor canal at its apex. Synonym: trigonum femorale, fossa scarpae major, Scarpa's triangle, subinguinal triangle. (05 Mar 2000) |
| Koch's triangle | A triangular area of the wall of the right atrium of the heart, that marks the situation of the atrioventricular node. (05 Mar 2000) |
| urogenital triangle | The anterior portion of the perineal region containing the openings of the urethra and vagina in the female and the urethra and root structures of the penis in the male. Synonym: regio urogenitalis, urogenital region. (05 Mar 2000) |
| Labbe's triangle | An area bounded below by a horizontal line touching the lower edge of the cartilage of the left ninth rib, laterally by the line of the false ribs, and to the right side by the liver; here the stomach is normally in contact with the abdominal wall. (05 Mar 2000) |
| laimer triangle | <anatomy> The triangular-shaped area of the cervical oesophagus bordered by the oblique fibres of the inferior constrictor muscle of the pharynx and the transverse fibres of the cricopharyngeus muscle through which Zenker's diverticulum occurs, and the A-V nodal triangle between the coronary sinus orifice and the ventricular crest. Synonym: laimer triangle. (05 Mar 2000) |
| Langenbeck's triangle | A triangle formed by lines drawn from the anterior superior iliac spine to the surface of the great trochanter and to the surgical neck of the femur; a penetrating wound in this area probably involves the joint. (05 Mar 2000) |
| frontal triangle | A triangle bounded above by the maximum frontal diameter and laterally by lines joining the extremities of this diameter with the glabella. (05 Mar 2000) |
| Lesser's triangle | The space between the bellies of the digastric muscle and the hypoglossal nerve. (05 Mar 2000) |